Neither pilot saw the other aircraft in time to avoid the collision. Risks associated with visual flight are well documented. These risks are known to be mitigated by radio position reporting; such reporting requires aircraft to be on a common frequency. Although both pilots were monitoring an appropriate frequency for the area they were in and for the type of operation they were conducting, neither pilot was on the same frequency. Independent flight operations in the same area, but operating on different frequencies, increases the risks associated with visual flight.Analysis Neither pilot saw the other aircraft in time to avoid the collision. Risks associated with visual flight are well documented. These risks are known to be mitigated by radio position reporting; such reporting requires aircraft to be on a common frequency. Although both pilots were monitoring an appropriate frequency for the area they were in and for the type of operation they were conducting, neither pilot was on the same frequency. Independent flight operations in the same area, but operating on different frequencies, increases the risks associated with visual flight. Both pilots were monitoring one or more radio frequencies that they considered appropriate for their location and intentions; however, neither pilot was on the same frequency, so any calls made were not heard by the other pilot. Neither pilot saw the other aircraft in time to avoid the collision and the two planes collided in flight.Findings as to Causes and Contributing Factors Both pilots were monitoring one or more radio frequencies that they considered appropriate for their location and intentions; however, neither pilot was on the same frequency, so any calls made were not heard by the other pilot. Neither pilot saw the other aircraft in time to avoid the collision and the two planes collided in flight.